During a real-time pass on Dec 9 the ACIS Digital Processing
Assembly Side-A (DPA-A) was detected in an unexpected
powered-off state. Engineering assessment indicated behavior
consistent with prior cases where the DPA powered-down. In each
of those cases a fault-tree analysis concluded the event was due
to a single event upset. The DPA was powered back on and the
required software patches reloaded during a real-time pass on
Dec 9. Recovery was complete at 7:13pm EST on Dec 9 with 29.1ks
of science loss. The scheduled observation of Abell 1795
Outskirts was impacted by the DPA-A shut-down and the lost science
time will be rescheduled in future weeks.